The invention relates generally to electrostatic precipitators and more specifically concerns the control of electrostatic precipitators.
An electrostatic precipitator removes the particulate matter from the smoke created by the burning of a fuel. The smoke is exposed to an electrostatic field, and the particles become electrically charged and migrate to the charged collecting surfaces creating the field. To maximize the collection of particulate, a precipitator should be operated at the highest practical field potential, the effect being to increase both the particle charge and the electrostatic collection field; however, the maximum field potential at which the precipitator can operate is limited by sparking and arcing which, if not controlled, can damage the precipitator and control system.
When the same type of fuel is burned continuously and the combustion is held relatively constant, the smoke is of a constant composition, and the magnitude of the electrostatic field for maximum particulate collection can be fairly constant. However, when a varying fuel such as refuse is burned or there are changes in the combustion, the composition of the smoke changes requiring corresponding changes in the magnitude of the electrostatic field. The point of maximum particulate collection cannot be held constant; therefore, an electronic control that can adjust rapidly to varying fuel and combustion is necessary to maintain precipitator efficiency.
It is therefore the primary object of this invention to provide an electronic control for electrostatic precipitators that can adjust rapidly and efficiently to varying fuel and combustion.
In the past a few of the electronic controls for electrostatic precipitators have reduced the power to the precipitators whenever a spark occurs and then increased the power along a fast ramp and then along a slow ramp until another spark occurs at which time the power is again reduced and the process repeated. These prior art controls apparently work well when the fuel and combustion are not varying. That is, these prior controls work well when the spark line remains constant or varies very little. However, whenever the spark line varies substantially, as a result of burning a varying fuel, these prior art controls are not efficient since their fast and slow ramp power curves do not provide a good fit to the spark line.
Hence, another object of this invention is to provide an electronic control for electrostatic precipitators in which after a spark power is reduced and then increased along fast and slow ramps that provide an efficient fit to the spark line even when the spark line is varying substantially.
A further object of this invention is to provide an electronic control for electrostatic precipitators in which after a spark power is reduced and then increased along fast and slow ramps whose slopes are dependent on the power at the time of the spark.
Still another object of this invention is to provide an electronic control for electrostatic precipitators which simply and efficiently detects open or short circuits in the power circuit to the precipitators.
A still further object of this invention is to provide an electronic control for electrostatic precipitators in which the number of sparks per minutes can be selected.
Yet another object of this invention is to provide an electronic control for electrostatic precipitators in which the power curve can be varied to more nearly fit the spark line.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.